As the main packaging material for the pharmaceuticals, polymer films have become increasingly important in daily life. However, affected by the production processes and physicochemical characteristics of the plastic films, the barrier properties of the plastic films to oxygen, water vapor, liquid substances, and other low molecular weight substances are difficult to meet the requirements of most drug packaging. The penetration of small molecular gases such as oxygen and water vapor into the packaging materials may cause the oxidation deterioration of the active ingredients in the drug, which gives rise to some phenomena like the proliferation of microorganisms, significantly shortening the shelf life of the drug. Therefore, the improvement of the barrier properties of plastic films to small molecular gases such as oxygen and water vapor and the possession of antibacterial properties are of great importance to improve the quality of the plastic films.
Graphene is a two-dimensional carbon nanomaterial, wherein each carbon atom connects with the other three carbon atoms to form covalent bonds by means of sp2 hybridization, and then arrange into a honeycomb hexagonal lattice. The remaining single electron 2P orbital of each carbon atom coincides with each other to form a delocalized conjugated π bond. The six-membered ring of the graphene has a pore size of only 0.15 nm which is smaller than that of helium, and has natural gas barrier properties. Meanwhile, the transmittance of the single-layered graphene to visible light reaches up to 97%, allowing that the single-layered graphene can be used to easily produce film materials with excellent light transparency under suitable process conditions. Also, the single-layered graphene has a thickness of only 0.34 nm and a width ranging from a few microns to tens of centimeters. The aforementioned characteristics and properties make graphene to be an ideal nanometer barrier material.
At present, one of the methods of using graphene to prepare a barrier material is to adopt a binder to bond the graphene film material and the polymer film substrate together. Nonetheless, due to the small contact area and a few reaction sites between the existing binders and the graphene, the safety and bonding strength are poor. Meanwhile, the adhesive strength of the existing binder is not changeable, which not only causes a high manufacturing cost of the binder, but also fails to meet the requirements of the packaging material for drugs.